Today's digital wireless communications systems packetize and then buffer the voice communications of wireless calls. This buffering, of course, results in the voice communication being delayed. For example, a listener in a wireless call will not hear a speaker begin speaking for a short period of time after he or she actually begins speaking. Usually this delay is less than a second, but nonetheless, it is often noticeable and sometimes annoying to the call participants.
Normal conversation has virtually no delay. When the speaker finishes speaking, a listener can immediately respond having heard everything the speaker has said. Or a listener can interrupt the speaker immediately after the speaker has finished saying something evoking a comment. When substantial delay is introduced into a conversation, however, the flow, efficiency, and spontaneity of the conversation suffer. A speaker must wait for his or her last words to be heard by a listener and then after the listener begins to respond, the speaker must wait through the delay to begin hearing it. Moreover, if a listener interrupts the speaker, the speaker will be at a different point in his or her conversation before beginning to hear what the listener is saying. This can result in confusion and/or wasted time as the participants must stop speaking or ask further questions to clarify. Thus, substantial delay degrades the efficiency of conversations.
However, some delay is a necessary tradeoff in today's wireless communication systems primarily because of the error-prone wireless links. To reduce the number of voice packets that are lost, leaving gaps in the received audio, wireless systems use well-known techniques such as packet retransmission and forward error correction with interleaving across packets. Both techniques require voice packets to be buffered, and thus result in the introduction of some delay. Today's wireless system architectures themselves introduce variable delays that would distort the audio without the use of some buffering to mask these timing variations. For example, packet delivery times will vary in packet networks due to factors such as network loading. Variable delays of voice packets can also be caused by intermittent control signaling that accompanies the voice packets and as a result of a receiving MS handing off to a neighboring base site. Thus, wireless systems are designed to tradeoff the delay that results from a certain level of buffering in order to derive the benefits of providing continuous, uninterrupted voice communication.
Buffering above this optimal level, however, increases the delay experienced by users without any benefits in return. Audio buffered above this optimal level is referred to as “audio overhang.” Such audio overhang can occur in wireless systems in certain situations. For example, variability in the time that some wireless systems take to establish wireless links during call setup can result in buffering with audio overhang. Because of the increased delay introduced by audio overhang, the quality of service experienced by these users can suffer substantially. Therefore, there exists a need for reducing audio overhang in wireless communication systems.